Article pubs.acs.org/est
Comparison of Sedimentary PAHs in the Rivers of Ammer (Germany) and Liangtan (China): Differences between Early- and NewlyIndustrialized Countries Ying Liu,† Barbara Beckingham,‡ Hermann Ruegner,ϕ Zhe Li,† Limin Ma,† Marc Schwientek,ϕ Huan Xie,§ Jianfu Zhao,*,† and Peter Grathwohl*,‡ †
State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China ‡ Center for Applied Geoscience, Eberhard Karls University of Tübingen, Hölderlinstrasse 12, 72074 Tübingen, Germany ϕ Water & Earth System Science Competence Cluster (WESS), Keplerstrasse 17, 72074 Tübingen, Germany § College of Surveying and Geo-informatics, Tongji University, Shanghai 200092, China S Supporting Information *
ABSTRACT: As a proxy to trace the impact of anthropogenic activity, sedimentary polycyclic aromatic hydrocarbons (PAHs) are compared between the early industrialized and newly industrialized countries of Germany and China, respectively. Surface sediment samples in the Ammer River of Germany and the Liangtan River of China were collected to compare concentration levels, distribution patterns, and diagnostic plots of sedimentary PAHs. Total concentrations of 16 PAHs in Ammer sediments were significantly higher by a factor of ∼4.5 than those in Liangtan. This contrast agrees with an extensive literature survey of PAH levels found in Chinese versus European sediments. Distribution patterns of PAHs were similar across sites in the Ammer River, whereas they were highly varied in the Liangtan River. Pyrogenic sources dominated in both cases. Strong correlations of the sum of 16 PAHs and PAH groups with TOC contents in the Liangtan River may indicate coemission of PAHs and TOC. Poor correlations of PAHs with TOC in the Ammer River indicate that other factors exert stronger influences. Sedimentary PAHs in the Ammer River are primarily attributed to input of diffuse sources or legacy pollution, while sediments in the Liangtan River are probably affected by ongoing point source emissions. Providing further evidence of a more prolonged anthropogenic influence are the elevated black carbon fractions in sedimentary TOC in the Ammer compared to the Liangtan. This implies that the Liangtan River, like others in newly industrialized regions, still has a chance to avoid legacy pollution of sediment which is widespread in the Ammer River and other European waterways.
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activities.3,4 Since economic growth is generally supported by energy consumption, PAH levels can indicate anthropogenic activities accompanying economic growth.5,6 For instance, PAHs in sediments have been shown to follow industrialization epochs in Europe7 and to track gross domestic product (GDP) and energy consumption in China.8,9
INTRODUCTION Contamination of the global environment by persistent organic pollutants (POPs) is one key feature of the chemical anthropocene of current day.1 Polycyclic aromatic hydrocarbons (PAHs) are one of the most ubiquitous classes of POPs globally and often occur at concentrations above thresholds that are considered to be detrimental to human and ecological health.2 Although PAHs have both natural and anthropogenic sources, anthropogenic sources typically dominate because of fuel combustion for energy supply involving transport, electrical power generation, and other industrial © 2012 American Chemical Society
Received: Revised: Accepted: Published: 701
August 14, 2012 December 14, 2012 December 19, 2012 December 19, 2012 dx.doi.org/10.1021/es3031566 | Environ. Sci. Technol. 2013, 47, 701−709
Environmental Science & Technology
Article
Figure 1. Locations of the Ammer River of Germany and the Liangtan River of China (a). Sampling locations of sediments in the Ammer River (b) and the Liangtan River (c), where in the inset sampling locations are arranged from C02 to C25 in numerical order.
Various research efforts have compared contrasting levels of contamination by POPs in different countries or regions and explored sources and environmental fate.10,11 For example, a study in the United Kingdom and Norway inferred that the difference in PAH concentrations in background soils might be a function of the forest type, proximity to PAH sources, and soil properties.12 Other researchers have collected literature values and compared PAH concentrations in atmosphere, soil, and sediment for several regions of the world, finding that higher PAH concentrations were frequently observed in areas with a long history of industrial activity or near centers of high population density.5,11,13 A novel perspective, however, is for a direct cross-catchment comparison of PAH contamination in early industrialized and newly industrialized countries. China is a newly industrialized country with an economy that has undergone rapid growth since economic reform in the late 1970s. In recent years, a large number of reports have focused on the environmental quality of China, such as in the atmosphere,14,15 soils,16−18 and sediments.19−21 In contrast, Germany is an early industrialized country, undergoing modern industrialization since the late 19th century. In 2010, Germany was ranked as the largest national economy in Europe and the fourth largest by nominal GDP in the world.22 Public policy in Germany has focused on good environmental quality in recent years, for instance, air quality and associated health impacts have improved since the 1990s,23 whereas cities in China have experienced increasing issues with meeting air quality standards for particulates.24−26 Germany and China may represent two countries in different stages in the evolution of industrialized economies. The goals of the current work are to a) compare the concentration levels, distribution patterns, and sources of sedimentary PAHs in a river in Germany and China, since sediments are an important sink of PAHs, b) to analyze the relationship between organic carbon/black carbon content and
PAH contamination in sediments, and c) to explore the environmental fate of PAHs in these systems. Findings are compared to sedimentary PAH levels compiled from a large number of recent studies in China (213 data points from over 60 water bodies in 54 publications) and Europe (127 data points from over 50 water bodies in 20 publications) to corroborate our observations (database compiled in the Supporting Information).
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MATERIALS AND METHODS Study Areas and Sample Collection. The locations of the rivers of Ammer and Liangtan are marked in Figure 1. The Ammer River in Germany (25 km long, with a catchment area of 165 km2) flows through some towns and cities (e.g., Herrenberg, Ammerbuch, Unterjesingen, and Tübingen) and then flows into the Neckar River which is a tributary of the Rhine River. The Liangtan River in China (89 km long, with a catchment area of 498 km2), also flows through some towns and cities (e.g., Baishiyizhen, Hanguzhen, Jinfengzhen, Chenjiaqiaozhen, Xiemazhen, and Beibei) and empties into the Jialing River, which is a major tributary of the Yangtze River. The rivers of Rhine and Yangtze are among the longest and most important rivers in Europe and in China, respectively, and the rivers of Ammer and Liangtan represent typical secondary tributaries of them, respectively. Population density in the catchments of Ammer and Liangtan is ∼600 and ∼400 inhabitants per square kilometers, respectively, as reported in 2010. The mean sedimentation rate in the upper reach of the Liangtan determined previously from sediment core 210Pb dating was 0.43 cm/year, although this may vary for different river segments and certain urban/industrial segments in the upper branch of the Liangtan may be disturbed by dredging9 and boating activities. In the Ammer, due to a constant contribution of large karst springs in the upper part of the 702
dx.doi.org/10.1021/es3031566 | Environ. Sci. Technol. 2013, 47, 701−709
Environmental Science & Technology
Article
Sample Analysis and Quality Control. Sample analyses in Germany and in China were similar and followed established methods. The method for sample processing involved Soxhletextraction followed by silica gel cleanup and quantification by gas chromatography with mass spectrometer detection (GCMS). Procedural blanks were performed periodically for quality assurance. Further experimental details were described previously27 and are summarized in the Supporting Information. Total Organic Carbon (TOC) and Black Carbon (BC). Measurement of TOC in Germany was performed with an elemental analyzer (Elementar Vario EL) after removal of carbonates, while TOC analysis in China was carried out using the Shimadzu TOC-Vcpn analyzer with a solid sample module (SSM-5000A). Black carbon content was measured following removal of organic carbon by thermal oxidation and inorganic carbon by acidification according to the CTO-375 method.28,29 More details can be found in the Supporting Information.
catchment discharge is rather stable. Direct runoff components become prominent only during heavy rainfall events but are generated mainly in the urbanized part of the catchment. Transport of resuspended sediments during high flow events can therefore result in some redistribution of sediments in the Ammer. More details (e.g., elevation, temperature, precipitation) of the two catchments are listed in Table 1. Table 1. Geographical and Geological Details of Two Catchments of Ammer (Germany) and Liangtan (China) Ammer catchment, Germany longtitude latitude min./max. elevation [m] area [km2] land use [%]a urban agricultural forested population density [inh/km2] geology mean air temperature [°C] mean precipitation [mm/a] mean discharge [m3/s] length of stream network [km] stream network density [km/km2] length of river [km] mean width of mainstream [m]
Liangtan catchment, China
8.82−9.11°E 48.53−48.56°N 315/600
106.24−106.45°E 29.42−29.82°N 178/936
165
498
17% 71% 12% 600
28% 33% 38% 400
Triassic; mainly karstic limestones and gypsum 8
Jurassic; mainly mudstones and sandstones 18
700
1100
1.1
6.4
171.4
236.4
1.0
0.5
25 5
89 20
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RESULTS AND DISCUSSION General Comments on the PAH Concentrations. The descriptive statistics of the total concentration of US EPA16 PAHs are illustrated in Figure 2. In the two rivers of this study,
a
Land use percentages of the Liangtan River catchment were calculated through the data of Landsat 7 ETM+ collected on March 14th, 2011.
The loading of sedimentary PAHs in these comparably sized rivers may represent both the past and ongoing contamination in the catchments. Surface sediment samples (top 5 cm) were collected along the rivers and tributaries of Ammer (N = 38) in June 2010 and Liangtan (N = 31) in November 2010, respectively. Sampling locations are shown in Figure 1b and Figure 1c, and sampling methods are described in the Supporting Information. PAH Components. Sixteen PAHs characterized by the US EPA as priority pollutants were analyzed, including naphthalene (Nap), acenaphthylene (AcNy), fluorene (Fl), acenaphthene (AcNe), phenanthrene (PhA), anthracene (An), fluoranthene (FlA), pyrene (Py), benz[a]anthracene (BaA), chrysene (Chy), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), indeno[1,2,3-cd]pyrene (IP), benzo[ghi]perylene (BghiP), and dibenz[a,h]anthracene (DBahA). Naphthalene-D8, acenaphthene-D10, phenanthrene-D10, chrysene-D12, and perylene-D12 were used as internal standards, and surrogate standards included fluorene-D10 and pyrene-D10. All chemical standards were obtained from SigmaAldrich.
Figure 2. Descriptive statistics of total concentrations of 16 PAHs in the rivers Ammer (Germany) and Liangtan (China) in this study and in comparison to levels in Europe and China reported in the literature (data provided in Table S1). The asterisks represent maximum and minimum values. The horizontal lines represent 5th, 50th, and 95th percentiles, and the boxes represent 25th and 75th percentiles.
levels of PAHs in sediments were highly variable between locations, ranging 3 orders of magnitude. The total concentrations in the Ammer River of Germany ranged from 112 to 22,900 ng/g dry wt. (average and median values: 8,770 ng/g and 7,040 ng/g), while those in the Liangtan River of China ranged from 69 to 6,250 ng/g (average and median values: 2,040 ng/g and 1,490 ng/g) and are very similar to a range reported by Feng et al.30 for sediments from the Yangtze River and tributaries. The average and median values in the Ammer River were 4.3 and 4.7 times higher, respectively, than those in the Liangtan River and the difference between the two rivers was found to be statistically significant by Student’s t test (p < 0.01). The contrast between concentrations in the Ammer 703
dx.doi.org/10.1021/es3031566 | Environ. Sci. Technol. 2013, 47, 701−709
Environmental Science & Technology
Article
Ammer River, 4-ring PAHs were abundant and dominated by FlA at ∼20% of total 16 PAHs. In the Liangtan River, 3- and 4ring PAHs dominated (in particular PhA at ∼15%), with a higher contribution of 3-ring PAHs as compared to the Ammer. We have used the distance between two percentiles to indicate variability in the percent contribution of PAHs to the total concentration. The 25th percentiles of individual PAHs were close to the 75th percentiles in the Ammer River with interquartile range (IQR) between 0.1 and 2.5%, indicating that percentages of PAHs were relatively stable among samples, especially for low molecular weight PAHs (IQR 2 rings, IQR 0.6−4.0%), especially for Nap (2 ring, IQR 10.1%) (Figure 3b). Distribution patterns for individual samples were arranged by ascending total concentration of 16 PAHs in Figure 4. The patterns of PAHs in the Ammer River were independent of concentration (e.g., comparable at 22,900 ng/g in G29 and at 270 ng/g in G11; see Figure 4a). Similar patterns of PAHs in sediments (this study), top soils, and atmospheric deposition samples that have been observed in southern Germany33 are also similar to distribution patterns in United Kingdom background soils reported by Nam et al.12 (Figure S2). This demonstrates that early industrialized countries, such as Germany and United Kingdom, are strongly affected by widespread nonpoint sources and legacy contamination that nowadays appears relatively diffuse. On the contrary, the patterns in the Liangtan River varied with total concentration of 16 PAHs (Figure 4b). Higher percentages of low molecular weight PAHs (e.g., Nap) were observed in samples with a lower level of PAH contamination (e.g., 143 ng/g in C26), whereas higher percentages of high molecular weight PAHs (e.g., FlA and Py) were in samples with a higher contamination level (e.g., 5,920 ng/g in C07). The variability of PAHs patterns in the Liangtan River sediments indicates that there are likely different sources of PAHs along the river. Thus, the sources of sedimentary PAHs appear relatively stable and diffuse in early industrialized countries (e.g., Germany) but relatively varied and ongoing in newly industrialized countries (e.g., China). Source Diagnostic Ratios of PAHs. Diagnostic ratios of PAHs are valid tools of PAH sources analysis because isomer pairs are diluted to a similar extent and distributed similarly to environmental media.34 Diagnostic ratios of PAHs can be applied to identify the possible emission sources.35 Ratios of An/(An+PhA) vs FlA/(FlA+Py) and BaA/(BaA+Chy) vs IP/ (IP+BghiP) in the rivers of Ammer and Liangtan are compared in Figure 5. The data of the Ammer River are clustered together, while those of the Liangtan River are dispersed over a wide range, further illustrating that source patterns of PAHs were relatively stable over location in the Ammer and highly varied in the Liangtan sediments. In the Ammer River, the ratios of FlA/(FlA+Py) were >0.5 and BaA/(BaA+Chy) were >0.35, indicating that combustion of biomass and coal were major sources of sedimentary PAHs. The ratio of IP/(IP+BghiP) from 0.30 to 0.47 implies the contribution of petroleum combustion. On the other hand, the ratio of An/(An+PhA) in the Ammer River covered a wider range, from 0.03 to 0.26 (Figure 5a). A low ratio (
